HYDRAULIC CONTROL SYSTEM OF 6-SPEED AUTOMATIC TRANSMISSION FOR VEHICLE

摘要

In order to provide an enhanced overall performance by achieving precise and effective control by providing a fail-safe function in two ways, a hydraulic control system of a six-speed automatic transmission includes a first clutch control portion, a first brake and third clutch control portion, a second clutch control portion, and a second brake control portion. The first clutch control portion controls a forward range pressure according to a control of a first proportional control solenoid valve so as to supply the forward range pressure to a first clutch at first, second, third, and fourth forward speeds and prevents hydraulic pressure from being supplied to the first clutch when the first proportional control solenoid valve is tumed-off at fourth, fifth, and sixth forward speeds. The first brake and third clutch control portion controls and selectively supplies the forward range pressure to a first brake or a third clutch according to a control of a second proportional control solenoid valve at the fourth, fifth, and sixth forward speeds, a low L range, and a reverse R range, and maintains a hydraulic line to the third clutch at the fourth, fifth, and sixth forward speeds in the case that an on/off solenoid valve controlling a spool valve controlling the hydraulic line to the third clutch malfunctions to be turned off. The second clutch control portion supplies a line pressure to a second clutch according to a control of a third proportional control solenoid valve at the third and fifth forward speeds and a reverse speed. The second brake control portion supplies the forward range pressure to a second brake according to a control of a fourth proportional control solenoid valve at the second and sixth forward speeds and controls an operating pressure of the second brake to be larger at the sixth forward speed than at the second forward speed.